Let us start with the easy stuff. There is already a forum post that explains how you can do several replaces in one shot. Please see
How do I do several replaces in one shot?Concerning the reformatting of dates it is more tricky.
It is easy to make a command that will add the slashes if your cursor is positioned at the start or at the end of a 6-digits number.
But it is more of a challenge if you want to process your complete file and examine all occurences of 6 digit numbers in a loop. It requires a Word macro using a find with wildcards. I can give you what I have come up with but I would rather say it is something for advanced users.